Bitcoins are a bubble commodity just like anything else that rapidly rises almost entirely because of speculation. In a sense the Bitcoin market is a lot like the current gold market, both are enjoying a massive boom fueled by demand for the product without any commercial reason to back up that demand, and the inevitable result of this is that values will at some point begin to plummet. The difference between Bitcoin and gold though is that even after gold plummets it will still retain highly respectable value, whereas when Bitcoin falls it's entirely possible for it to be completely devalued as a product.
The value of bitcoin is that it can be traded, easily, and can't be easily faked. Gold can't be easily faked, but it can't be traded so easily.
For a bitcoin to be completely worthless rather stretches the imagination. At a minimum they are a sort of geeky collector's item and inherently limited in supply. They also cost next to nothing to store.
